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Old 04-11-2009, 07:55 PM   #1
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Default Help me choose injectors

So, before anyone rips me apart, let me say that a guy can only do so much searching before his eyes start to bleed and this isn't the only thing or place I've searched. So if this has been addressed, please forgive me and either give me an answer or link to where I can find an answer.

1.6 with a 15g and intercooler. The goal is 275+hp. I will be using a MS when the time comes. This is a race car and is not driven on the street and I would like to run straight e85. I've already researched e85, so I don't need opinions on if I should run it or not, only with choosing injectors.

I've mostly worked on older cars and have never tuned a stand alone ecu, so I don't know what the capabilities are exactly. I used an injector calculator that tells me that I should use 600cc injectors to support 275hp at 80% duty cycle. E85 requires 30% more fuel for burn which would mean I would need at least 750cc injectors. However, I doubt this calculator takes into consideration that I can increase the duration of the injector. I only had 550s in my DSM with 400hp. So the question is, how big do I need to go to run E85 for a 275-300hp engine?
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Old 04-11-2009, 10:07 PM   #2
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Mike,

I just installed a set of Deatschwerks 600's. They are PnP and worked great. They just went off group buy price of $289 and IIRC are $329 or $349 now. These are new injectors that have been match flowed.

EDIT:

I just saw you said E85. Deatschwerks also had 750's for the same $. They amay be out of stock right now, though, try PM'ing Mark. They are also working on some 1000's. 600's would be the absolute floor for E85, and even then be touchy. I would err on the side of 750's.
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Old 04-12-2009, 11:55 PM   #3
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What BSFC did you specify on the calculator? .60? I think at that power range youll want to calculate for .65 if I'm not wrong.
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Old 04-13-2009, 12:31 AM   #4
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I also believe the Bsfc you should be calculating is .60 to .65. I am pretty sure you will need at least a 680cc bare minimum but i would opt for 750cc or 1000cc if you have the engine management to run the larger injectors and still have a decent idle. Just remember you also want to end up going faster and dont want to buy injectors again.
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Old 04-13-2009, 12:46 AM   #5
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Quote:
Originally Posted by Chris_Himself View Post
What BSFC did you specify on the calculator? .60? I think at that power range youll want to calculate for .65 if I'm not wrong.
I did .65, but that does not factor in the extra 30% required from e85. So I put in .85 and it looks like I'd need 750cc injectors minimum. What I'm not sure about is how to figure in the pulse width. Can I run 600s, but extend the duration by 30% to compensate? Sure, I can buy huge injectors. I'm just trying to figure it if I HAVE to.
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Old 04-13-2009, 12:49 AM   #6
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Originally Posted by kww502 View Post
but i would opt for 750cc or 1000cc if you have the engine management to run the larger injectors and still have a decent idle.
I'm not worried about the idle as long as it will run. It won't see any street time. The DSM racecar I had needed to idle at 2k to stay running - no stand alone.
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Old 04-13-2009, 12:56 AM   #7
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You need to post up a build thread.
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Old 04-13-2009, 01:08 AM   #8
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Before you take care of boosting the car on E85, you will need to take incremental steps.

Are your lines and seals E85 friendly? I've heard some stuff about E85 eating away at the injector o-rings. Do some searching
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Old 04-13-2009, 04:36 AM   #9
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Just do 1000cc's and be done with it.
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Old 04-13-2009, 10:08 AM   #10
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Quote:
Originally Posted by Chris_Himself View Post
Before you take care of boosting the car on E85, you will need to take incremental steps.

Are your lines and seals E85 friendly? I've heard some stuff about E85 eating away at the injector o-rings. Do some searching
What part of "I've already researched e85, so I don't need opinions on if I should run it or not, only with choosing injectors." didn't you understand?
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Old 04-13-2009, 10:09 AM   #11
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Originally Posted by Stein View Post
You need to post up a build thread.
I've been thinking that. I need to get some pictures of where the car is now. I'll try to do that tonight, start a thread, and post a link in this one.
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Old 04-13-2009, 11:31 AM   #12
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Quote:
Originally Posted by omaharam View Post
I doubt this calculator takes into consideration that I can increase the duration of the injector. I only had 550s in my DSM with 400hp. So the question is, how big do I need to go to run E85 for a 275-300hp engine?
what the heck do you think "duty cycle" means?

you can increase the duration of the injector to 80% duty cycle. that means at your maximum RPM, the injector pulse can only be 80% as long as the cylinder cycle at that RPM (assuming sequential injection).

the only way to increase fuel delivery for a given injector at its maximum safe duty cycle is to increase rail pressure--which is probably how your DSM was running such tiny injectors for 400 hp.
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Old 04-13-2009, 01:03 PM   #13
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Quote:
Originally Posted by y8s View Post
what the heck do you think "duty cycle" means?

you can increase the duration of the injector to 80% duty cycle. that means at your maximum RPM, the injector pulse can only be 80% as long as the cylinder cycle at that RPM (assuming sequential injection).

the only way to increase fuel delivery for a given injector at its maximum safe duty cycle is to increase rail pressure--which is probably how your DSM was running such tiny injectors for 400 hp.
Hmmm...guess I forgot that the formula asks for a duty cycle.

Actually the reason we were probably getting away with it on the DSM is cuz we were running 118 octane fuel with pulled timing.

THanks for the help guys.
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Old 04-14-2009, 12:17 AM   #14
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Quote:
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You need to post up a build thread.
Build thread.

https://www.miataturbo.net/forum/t33980/
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Old 04-14-2009, 02:34 PM   #15
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If you want to run E85, i suggest not doing anything less than 900/1000cc's, just to make sure you have a little room to grow
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